Method for creating a joint between the exciter poles and the pole casing of an electric machine

ABSTRACT

The method of making a joint connection between exciter poles and the pole housing of an electrical machine includes positively displacing material of the pole housing ( 10 ) pointwise by means of the joining tool into a recess ( 22 ) provided in each of the exciter poles ( 12 ) at respective joining points to make a form- and force-locking connection of the exciter poles with the pole housing.

BACKGROUND OF THE INVENTION

The invention relates to a method for producing a joint connection, inparticular between exciter poles and the pole housing of an electricalmachine, as well as an electrical machine produced by that method.

In electrical machines that have an electric excitation, it is known tosecure the exciter poles that carry the exciter winding to the inside ofa substantially cylindrical pole housing. Securing the exciter poles tothe pole housing can be accomplished in a known way, for instance bymeans of a screw connection, welded connection, or adhesively bondedconnection. In addition, a method is known from French PatentApplication FR 2 488 749, in which exciter poles are secured to the polehousing by means of a force-locking joint connection, in which materialof the pole housing is positively displaced into a conical recess of theexciter poles. A disadvantage of this is that the conical recesses canbe produced only with great effort using precision tools. To achieveuniform, reliable positive displacement of the material of the polehousing into the conical recess of the exciter poles, which widenstoward the bottom, high-precision and thus complicated and expensiveadjustment of the joining tools relative to the recess is necessary.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method of makingarticulated connections between exciter poles and a pole housing of anelectrical machine and to provide an electrical machine made by thatmethod which does not have the above-described disadvantage.

The method of making the joint connection between the exciter poles anda pole housing of an electrical machine by means of a joining toolincludes providing an exciter pole having a recess at a joining point ona pole housing and positively displacing material of the pole housingpointwise by means of the joining tool into the recess of the exciterpole at the joining point to make a form- and force-locking connectionof the exciter pole with the pole housing.

With the method of the invention, it is possible by comparison, in asingle way, to establish a form- and force-locking connection betweenthe exciter poles and the pole housing, in which a secondary air gapbetween the exciter poles and the pole housing is reduced to a minimum.Because the material of the pole housing and of the respective exciterpole is positively displaced by the joining tool pointwise at at leastone joining point into a corresponding recess of the exciter pole, aforce-locking connection between the exciter poles and the pole housingcan be attained by means of simple method steps, which can moreover, beperformed using a tool of simple construction. High joining forces arebrought to bear, which over the long term assure large-area contact ofthe exciter poles with the pole housing. By imposition of the highjoining forces, the gap between the exciter poles and the pole housingis reduced to its technologically feasible minimum. The merely pointwisepositive displacement of the material of the pole housing into acorresponding recess of the exciter poles assures that the material lossof the exciter poles is extremely slight, thereby essentially precludingan impairment of these electromagnetic properties.

Advantageous features of the invention will become apparent from thecharacteristics recited in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWING

The objects, features and advantages of the invention will now beillustrated in more detail with the aid of the following description ofthe preferred embodiments, with reference to the accompanying figures inwhich:

FIG. 1 is a schematic cross-sectional view through a connection pointbetween an exciter pole and a pole housing prior to joining operation;

FIG. 2 is schematic cross-sectional view through a connection point ofFIG. 1 after completion of the joining operation;

FIG. 3 is a diagram of a micrograph of the joining point of theinvention;

FIG. 4 is a cross-sectional view of another embodiment of a connectionpoint prior to the joining operation,

FIG. 5 is a cross-sectional view through a connection point of FIG. 4after the joining operation;

FIG. 6 is a cross-sectional view of an additional embodiment of aconnection point prior to the joining operation, and

FIG. 7 is a cross-sectional view through a further embodiment of anexciter pole.

FIG. 1 in a sectional view shows a detail of a pole housing 10 and anexciter pole 12 of an electrical machine not shown in its entirety. Theelectrical machine as a rule has four or six exciter poles 12, which aredisposed along the inside circumference of the cylindrically embodiedpole housing 10. The fragmentary view of one exciter pole 12 is intendedfor purposes of clear illustration of the method for producing a jointconnection between the pole housing 10 and the exciter poles 12. Theexciter poles 12 are disposed over the circumference of a mandrel 14,which is a component of a joining apparatus. The exciter poles 12 areprovided beforehand with the exciter windings, not shown here, andlocked in a suitable way over the circumference of the mandrel 14. Themandrel 14 with the exciter poles 12 is then moved into the pole housing10. In this process, either a relative motion of the mandrel 14, havingthe exciter poles 12, to the pole housing 10 or a relative motion of thepole housing 10 to the fixedly positioned exciter poles 12, or both canoccur. The joining apparatus also has a tool holder 16, which has atleast one tool guide 18 for a joining tool 20. The joining tool can besubjected to a joining force F by means of a suitable device, such as ahydraulic or pneumatic device.

Positioning of the pole housing 10 and/or of the mandrel 14 having theexciter poles 12 is done in such a way that one recess 22 madepreviously in the exciter poles 12 is associated with each joining tool20. In a preferred exemplary embodiment, the joining tool 20 is acircular die, with which a corresponding bore 24 (recess 22) is thusassociated. The bore 24 may—as shown in FIG. 1—be embodied as a throughbore, and in a further exemplary embodiment it may be a blind bore.Moreover, in exemplary embodiments not shown, the contours correspondingto one another of the joining tool 20 and the recess 22 may have otherthan a circular shape. For instance, oval or polygonal cross sectionsare possible. Moreover, more than one recess 22 may be provided perexciter pole 12, in which case the recesses are spaced apart axiallyfrom one another, for example. For such an embodiment, the joiningapparatus then has a suitable number of joining tools 20.

The joining tool 20 is embodied with two stages; that is, it has a firstportion 26 of smaller diameter and an adjoining portion 28 of largerdiameter. The portions 26 and 28 merge with one another via an annularshoulder 30. The annular shoulder 30, in the example shown, is disposedat a right angle to the action of the joining force F. In otherexemplary embodiments, not shown, the annular shoulder 30 may have aconical shape.

Once the exciter pole 12 or pole housing 10 is positioned, the joiningtool 20 is acted upon by the joining force F. This presses the polehousing 10 against the exciter poles 12. The mandrel 14 serves as athrust bearing for the joining force F. In a first method step, thejoining tool 20 with its portion 26 touches the pole housing 10 and inthe process positively displaces a certain quantity of material of thepole housing 10—depending on the dimensioning of the portion 26—into therecess 22 located opposite the joining tool 20. Maintaining the joiningforce F puts the annular shoulder 30 into touch contact with the polehousing 10, so that the joining force F is now introduced into the polehousing 10 via the larger-diameter portion 28. The result isthus—depending on the size of the annular shoulder 30—an additionaltwo-dimensional pressure on the pole housing 10, so that an upper edge32 of the recess 22 is forced into the recess 24 in response to thejoining force F. This forcing of the edge 32 into the recess 22, asshown in further detail in FIG. 2, undercuts the material previouslypositively displaced via the portion 26 of the joining tool 40, and thismaterial forms a rivet 34. It is clear from the finished jointconnection shown in FIG. 2 that as a result of the undercut 33 of theedge 32, which is made of the material of the exciter pole 12, the rivet34 positively displaced from the material of the pole housing 10 isfirmly fastened in place. As a result of the strong forces occurringduring the joining according to the invention, the exciter poles 12 arepositively displaced in the direction of the pole housing 10, so that agap 35 remaining between the exciter poles 12 and the pole housing 10remains limited to its technically feasible minimum.

The form- and force-locking connection between the exciter poles 12 andthe pole housing 10 is durably preserved even after removal from thejoining apparatus. Because the recess 22 and the joining tool 20 are forinstance embodied as circular, the rivet 34 is constricted, or in otherwords undercut, along a circumferential line along the edge 32. Thusforces engaging in the axial direction of the exciter poles can also bereliably absorbed during the intended use of the electrical machinewithout causing loosening and thus an enlargement of the gap 35.Depending on the number of connection points selected between 1 exciterpole 12 and the pole housing 10, a secure, firm connection can bedurably assured.

The micrograph of the connection point between the pole housing 10 andthe exciter pole 12 shown in FIG. 3 clearly shows how the edge 32undercuts the rivet 34. It has been positively displaced into the rivet34 from the material of the pole housing 10.

In FIGS. 4 and 5, a further variant embodiment for making a jointconnection between the exciter pole 12 and the pole housing 10 is shown.Identical elements to those of FIG. 1 are identified by the samereference numerals and will not be explained again. For the sake ofsimplicity, the joining apparatus has not been shown. It is clear fromFIG. 5 that the recess 22 may be embodied as a blind bore 36. Veryadvantageously, the blind bore 36 can be introduced into the exciterpole 12 by means of a so-called pan, whereupon the edge 32 issimultaneously thrown out in the form of a bead 38 encompassing therecess 22.

From the joint connection shown in FIG. 4 between the pole housing 10and the exciter pole 12, it becomes clear that in the joining operation(here the joining can be done with a single-stage swaging die 20 a) thebead 38 is positively displaced into the recess 22 by the joining forceF, so that the rivet 34 positively displaced into the recess 22 by thejoining tool is likewise constricted or undercut by the edge 32 of theexciter pole 12. Thus once again a durable form- and force-lockingconnection between the exciter poles 12 and the pole housing 10 ispossible. The rivet 34 is firmly fastened in place by the undercut 33,and once again a tensile force between the pole housing 10 and theexciter poles 12 is built up, so that the gap 35 is still reduced to itsminimum. This averts the creation of secondary air gaps.

FIG. 6 is a schematic illustration through a further joint connection.Once again, identical elements are provided with the same referencenumerals and not explained again. In the exemplary embodiment shownhere, the recess 22 of the exciter pole 12 is once again embodied as athrough bore. During the joining process explained in conjunction withFIGS. 1-3, when the joining force F engages the recess 22 a counterpartdie 40 is stopped, which on its end toward the pole housing 10 has aconical bevel 42. The effect achieved by this is that during thejoining, the material of the pole housing 10 that forms the rivet 34 andis positively displaced into the recess 22 runs up against the conicalface 42 of the counterpart die 40 and is positively displaced laterally.Once again, this creates the undercut 33, which assures a secure form-and force-locking connection between the exciter pole and the polehousing 10.

A further variant embodiment of the recess 22 of the exciter pole 12 isshown in FIG. 7. Here, for the sake of clarity, only the exciter pole 12is shown in a sectional view. The recess 22 is embodied as a steppedbore 44, which on its side toward the pole housing 10 merges via ashoulder 46 with a smaller-diameter portion. The result attained is thatthe positively displaced material of the pole housing 10 that forms therivet 34 is positively displaced underneath the shoulder 46, when itruns up against a counterpart die not shown here, so that once again anundercut 33 is created.

In summary, it becomes clear that it is a common feature of all theexemplary embodiments that by means of an easily performed so-calledswage riveting or punch riveting operation, a simple and durable jointconnection between the exciter poles 12 and the pole housing 10 can becreated, which in particular by the embodiment of an undercut 33 isdurably form- and force-locking. The embodiment of the undercut 33 canbe attained by means of a special embodiment of either the recess 22 orthe joining tool 20 or both. In all the exemplary embodiments, the jointconnection is established in both force- and form-locking fashion withonly a single working stroke of the joining tool embodied as a swagingdie.

What is claimed is:
 1. A method of making a joint connection betweenexciter poles and a pole housing of an electrical machine by means of ajoining tool, said method comprising the steps of: a) providing anexciter pole (12) having a recess (22) at a joining point on a polehousing (10); and b) positively displacing material of the pole housing(10) and of the exciter pole (12) pointwise by means of joining tool(20) into said recess (22) of said exciter pole (12) at said joiningpoint to make a form- and force-locking connection of the exciter pole(12) with the pole housing (10).
 2. The method as defined in claim 1,wherein the material of the pole housing (10) is positively displacedinto the recess (22) by punch riveting using a die (20).
 3. The methodas defined in claim 1, further comprising positively displacing an outeredge (32) of the recess (22) of the exciter pole (12) into the materialof the pole housing (10).
 4. The method as defined in claim 2, whereinsaid die is a two-stage swaging die (20).
 5. The method as defined inclaim 1, wherein said exciter pole (12) is provided with a bead (38)extending circumferentially around an outer edge (32) of the recess (22)and said bead (38) is at least partially positively displaced into thematerial of the pole housing (10) which forms a rivet (34).
 6. Themethod as defined in claim 5, further comprising making the recess (22)in the exciter pole (12) and creating said bead (38) during the makingof the recess (22).
 7. The method as defined in claim 1, wherein saidrecess (22) is a blind bore (36).
 8. The method as defined in claim 1,wherein said recess (22) is a throughgoing bore (24).
 9. The method asdefined in claim 1, wherein said positively displacing said material ofsaid pole housing occurs by means of a joining force (F) and furthercomprising applying a retaining force counter to said joining force bymeans of an assembly support of the exciter pole.
 10. A method of makinga joint connection between exciter poles and a pole housing of anelectrical machine by means of a joining tool, said method comprisingthe steps of: a) providing an exciter pole (12) having a recess (22) ata joining point on a pole housing (10); and b) positively displacingmaterial of the pole housing (10) and of the exciter pole (12) pointwiseby means of joining tool (20) into said recess (22) of said exciter pole(12) at said joining point to make a form- and force-locking connectionof the exciter pole (12) with the pole housing (10), so that a rivet(34) is displaced into said recess (22) from the pole housing (10) andan edge (32) of the recess (22) is displaced into a recess (24) during ajoining process, and also an undercut (33) of the rivet (34) isproduced.